1. Field of the Invention
The present invention relates to a reinforcing member structure for a vehicle body of an automobile, a motorcycle or the like.
2. Description of the Related Art
Conventionally, for example, a reinforcing member structure for a vehicle body of an automobile is known, in which a steering hanger member (a reinforcing member) connecting left and right front pillars to each other is formed of a pipe material (see Japanese Patent Application Laid-open No. 8-119001). In designing the reinforcing member, a consideration is given so that the reinforcing member does not resonate with the vibration of a vibrating source such as an engine or the like.
More specifically, if the natural vibration frequency of the reinforcing member corresponds to the vibration frequency of the vibrating source, the reinforcing member is violently vibrated by resonance to provide an uncomfortable feeling to an occupant in the vehicle. To prevent such resonance from being produced, considering that the natural vibration frequency of the reinforcing member is proportional to the rigidity of the reinforcing member, it has conventionally been proposed that the thickness of the pipe material forming the reinforcing member is increased, or the diameter of the pipe material is increased, thereby to enhance the rigidity thereof to the utmost, so that the natural vibration frequency may exceed the usual vibration frequency of the vibrating source.
However, if the thickness of the pipe material is increased, or if the diameter of the pipe material is increased, a large increase in weight is brought about, which is not preferred. In addition, in carrying out the development, expensive various pipe materials must be prepared for the rigidity and vibration tests, resulting in a problem of a largely increased development cost.
Accordingly, it is an object of the present invention to provide a reinforcing member structure for a vehicle body, wherein the rigidity of the reinforcing member can be effectively enhanced, while suppressing the increase in weight to the utmost, and the development cost can be suppressed to a low level.